The present invention relates generally to communications systems, and more specifically to a communications system in which switching nodes are interconnected by regular and spare (alternate) routes and in which a multidrop control network is formed, the topology of the multidrop control network being reconfigurable in the event of a line fault in the system.
A known data communication system comprises a network management center and a plurality of switching nodes each serving one or more user data terminals. The switching nodes and the network management center are interconnected by regular and spare transmission lines. Each transmission route includes a plurality of data channels which are connected to the data channels of other routes to form a data network for carrying users' signals. A management control channel is preassigned in each route for carrying a network management signal. The management control channels of regular routes are interconnected at the nodes so that a management control network is formed independently from the data network to transmit a network management signal from the center to each node. In addition to the management network, a system control channel is preassigned in each of the regular and spare routes. Each system control channel is connected to the system control channels of other regular and spare routes to form a system control network. In the event of a line fault in some route, control signals are exchanged between nodes through the system control network to reconfigure the system control network using a spare route instead of the faulty route. Since individual control channels are used for carrying signals other than data signals, it is desired to improve the utilization efficiency of the communications system.